This invention relates to a measurement while drilling tool. More specifically, but without limitation, this invention relates to an apparatus and method for telemetering a down hole parameter from a well.
Operators drill wells many thousands of feet in the search for hydrocarbons. The wells are expensive and take a significant amount of time to plan. Operators find it important to obtain data about the various subterranean reservoirs once the actual drilling begins. Thus, measurement while drilling (MWD) tools have been developed that gather information about the subterranean reservoirs and telemetry the data to the surface. Engineers and geologist can then use this data in an effort to understand the formations and make plans on completion, sidetracking, abandoning, further drilling etc.
MWD tools are expensive tools due to their complexity. The tools are designed for a lifetime of 5-7 years, and the tools are routinely made of expensive materials and electronics which require a lot of maintenance by highly trained personnel. Typically, service companies have geographically positioned regional maintenance facilities that perform these tasks. As the use of MWD and LWD tools expanded, several problems have become evident. One problem is that maintenance requires very high levels of training. Mean time between failures (MTBF) has become the standard measurement for evaluating the reliability of the MWD technology, and a central question is when will the tool fail. Another problem is that the maintenance facilities require large spaces and expensive testing equipment. It is not uncommon for a MWD tool to spend as much time traveling to and from these maintenance facilities as it does at the wellsite. In one study, it was found that a MWD tool string spends less than 90 days a year in a well, and the maintenance and logistics cost of a MWD tool can amount to 50% of the annual expense of the system.
Therefore, it is an object of the present invention to reduce the maintenance and repair time of MWD tools. It is also an object of the present invention to reduce the maintenance and repair cost. It is also an object to manufacture a tool that is less expensive to build, less complex and have higher reliability. These objects, and many others, will be met by the following disclosure.